1. Field
The invention is in the field of irradiating various materials, such as foods, particularly meat, with electrons to beneficially alter the characteristics of such materials, as for example to reduce or kill pathogens in foods.
2. State of the Art
The generation of high power electron beams for irradiating various materials has-long been known and used both for possible military purposes and for civilian purposes. It has been used commercially for modifying polymers and for sterilizing medical products and hospital wastes. The presence of pathogens, such as E-coli or salmonella bacteria, in meat, and especially in massed particles of meat, such as extensively used by the fast food burger industry, has long been recognized and procedures undertaken largely on an experimental basis to rid such food items of the pathogens contained therein, or at least to considerably reduce the pathogen content thereof. The use of linear electron accelerators for the purpose has been suggested, and known equipment has been employed to a limited extent.
As early as December 1948, Brasch U. S. Pat. No. 2,456,909 disclosed that the exposure of various types of meat to high speed electrons in a series of repetitive pulses would sterilize meat and, if the meat was first frozen and if exposure to the electrons was done in the absence of air, changes in taste, odor, and appearance of the meat would be avoided. A later patent to Silverman et al., U.S. Pat. No. 3,567,462 of March 1971 discloses the use of ionizing radiation for extending the storage life of fresh animal tissue. However, a patent to Glyptis No. 3,876,373 of April 1975 mentions electron beam sterilization as prior art but rejects it for a variety of reasons, including alteration of taste and appearance of food to which the procedure is applied.
An account of a successful commercial operation in France, using a linear accelerator to eliminate pathogens by the irradiating of chicken meat that had been mechanically separated from bone particles, is contained in the scientific journal "Radiation Physical Chemistry" Vol. 36 No. 3 pp. 661-665 (1990). This was apparently the first application of radiation for sterilizing chicken meat on a commercial scale. There, mechanically deboned chicken meat was pressed into slabs and exposed to irradiation by a linear electron accelerator, first on one side of the slab and then, in a second run through the equipment, on the opposite side of the slab.
A very recent U.S. Pat. No. 5,366,746 of Nov. 22, 1994 to Von T. Mendenhall assigned to Utah State University discloses the use of electron beam radiation (EBR) at doses between about 1.0 to 20 Kgys applied to thermally pre-processed meat for sterilization and other purposes.